Physical Features and Drainage of West Africa – Lecture 2

Question-and-Answer flashcards covering geological structure, relief zones, drainage patterns, and case-study dams in Ghana and Nigeria as discussed in Lecture 2.

What are the two main geological components of West Africa and how old are they?

Ancient cratons (>1,500 million years) and younger orogenesis belts (~1,200 million years).

Which four key minerals are commonly found in West Africa’s cratonic regions?

Gold, diamonds, asbestos, and iron.

Which metals are typically associated with West Africa’s orogenesis zones?

Copper, lead, zinc, and tin.

During which geological era were most West African relief features formed?

The Precambrian era.

What are the four broad relief zones of West Africa?

West African Coast, Coastal Plain, Plateau, and Highlands.

How would you characterise the general coastline of West Africa?

Low, sandy, relatively smooth, with few natural harbours but extensive lagoons.

Why are natural harbours scarce along the West African coast?

Because sand deposition creates smooth, bar-built shorelines that lack deep, sheltered inlets.

What physical process contributes to the smooth coast north of Dakar?

Deposition of Saharan sand transported by wind and currents.

Why are the coasts of Togo, Benin, and Nigeria especially smooth and sandy?

Continuous sand-bar deposition along the Gulf of Guinea shoreline.

How extensive are the coastal plains of West Africa overall?

They are generally narrow and occupy only a small proportion of the sub-region.

In which three countries are West Africa’s coastal plains most expansive?

Gambia, Senegal, and Mauritania.

What major relief feature limits inland spread of the coastal plains?

The interior plateau system.

Where does the West African Plateau reach its greatest height?

At its western (Futa Jallon) and eastern (Jos Plateau) extremities.

Name the two key plateau areas that form the western and eastern high points.

Futa Jallon Plateau (west) and Jos Plateau (east).

How have rivers such as the Niger and Oti modified the plateau landscape?

They have cut through the plateau, creating valleys and gaps that interrupt the plateau continuity.

Give two examples of volcanic or isolated highlands in West Africa.

Guinea Highlands and the Cameroon/Bamenda Mountains.

List three additional highland systems besides the volcanic peaks.

Akuapim-Togo-Atacora ridges, Cameroon Highlands, and Adamawa Highlands.

State three positive contributions of relief features to West African development.

Induce rainfall, provide river sources and construction materials, host mineral resources, and offer transport corridors.

Name three ways relief can impede development in West Africa.

Hinders transport network construction, contributes to flooding, and can trigger earthquakes or other hazards.

Where in West Africa do the steepest slopes and heaviest rainfall coincide?

The south-west sub-region (Guinea, Sierra Leone, Liberia).

Into which two major marine bodies do most West African rivers discharge?

The Atlantic Ocean and the Gulf of Guinea.

Outline the general course of the River Niger.

Originates in Futa Jallon Highlands, flows northeast, bends southeast, then turns south to enter the Atlantic at the Niger Delta.

Why are many West African rivers of limited navigational value?

Seasonal flow fluctuations, rapids, and sand bars at estuaries restrict continuous navigation.

Give an example of West Africa exploiting river potential for hydropower.

Ghana’s Akosombo and Bui dams on the Volta River system.

What was the first structure completed under Nigeria’s Niger Dams Project?

The Kainji Dam (completed in 1968).

Name two benefits provided by the Niger Dams Project.

Generates electricity for major Nigerian cities and supports irrigation/fishing through its reservoir.

Identify one major challenge facing the Niger Dams Project.

Drought-induced variability in Niger River flow reduces hydro-electric output.

Which river feeds Ghana’s Bui Dam, and what is its installed generation capacity?

The Black Volta; designed for 400 MW (operational output ~100 MW supplied to the grid).

State two national benefits of the Bui Dam Project.

Adds a reliable energy source and supplies additional water to the Akosombo reservoir; also supports irrigation and fishing.

Mention one negative socio-economic impact linked to the Bui Dam.

Displacement and livelihood loss for farming and fishing communities in the reservoir zone.